1. Background of the Invention
The present invention relates to an apparatus for forming a dry coat of the lubricant for cold forging on cold plastic working materials (e.g., rod, tubular, plate and other shaped members, sintered materials, etc., made of steel, titanium, titanium alloy, copper, copper alloy, aluminium, or aluminium alloy), which are cold forged by using a pressing machine.
2. Description of the Prior Art
Recently employed process applied to cold forging of the cold plastic working materials includes is forming thereon a dry coat of the lubricant for cold forging. Specifically, the process includes heating the cold plastic working materials to a predetermined temperature, applying water dry type lubricant on the heated materials, and applying heated air stream of a temperature higher than that of the cold plastic working materials, thereby drying the lubricant applied on the materials.
The above process, which includes drying the cold plastic working materials heated to a predetermined temperature by the application of the heated air stream having a temperature higher than that of the material, poses a problem that the cold plastic working materials are heated to an excessively high temperature. This excessively high temperature of the materials may shorten the life of a metal mold in the pressing machine when the materials for cold plastic working of such an excessively high temperature is fed to the pressing machine. To avoid this problem, a material cooling time is needed to lower the temperature of the cold plastic working materials prior to being fed to the pressing machine.
To heat the cold plastic working materials to a predetermined temperature in a conventional manner, a heating chamber is disposed in a conveying line of the cold plastic working materials, through which the cold plastic working materials successively pass, so that they are heated under a high temperature atmosphere within the heating chamber. This conventional heating arrangement inherently requires a lengthened heating chamber extending along the conveying path so as to heat the cold plastic working materials during the conveyance of the cold plastic materials at a usual transfer speed. However, when the heating chamber is to be installed in a limited space, it may not have a sufficient length, with the result that the transfer speed needs to be lowered to allow the cold plastic materials to stay within the heating chamber for a prolonged period of time.
In either way, a prolonged period of time is needed for forming lubricant dry coat, which is disadvantageous in the fact that such a lower coat-forming speed cannot match the operation speed of the pressing machine.
Therefore, it is an object of the present invention to provide a lubricant coat forming apparatus that is capable of forming a dry coat at a sufficient speed to match the operational speed of the pressing machine.
Extensive efforts have been devoted by the present inventors to achieve the above object. These efforts have led to the finding of the fact that the temperature of the air stream for drying the coat affects on the dry time. Upon such a fact, the present inventors have obtained the knowledge that cooling air stream would be suitable for shortening a coat drying time rather than using a hot air stream, and hence achieved the present invention.
Specifically, according to one aspect of the present invention, there is provided a lubricant coat forming apparatus for forming a dry coat of water dry type lubricant on the surface of each of cold plastic working materials. The apparatus includes a heating unit for heating the cold plastic working materials to a predetermined temperature, a lubricant applicator for applying the lubricant on the surfaces of the cold plastic working materials heated at the heating unit, and a drying unit for drying the lubricant applied on the surfaces of the cold plastic working materials by applying cooling air stream to the cold plastic working materials. The cooling air stream has a temperature lower than that of the cold plastic working materials heated by the heating unit.
By xe2x80x9cheating the cold plastic working materials to a predetermined temperaturexe2x80x9d, it is meant that the cold plastic working materials are heated to a temperature higher than the atmospheric temperature (e.g., not less than 60xc2x0 C.). By xe2x80x9cthe air stream has a temperature lower than that of the cold plastic working materials heated by the heating unitxe2x80x9d, it is meant that the air stream has a temperature lower than that the temperature (predetermined temperature) of the cold plastic working materials themselves, which have been heated by the heating unit. For example, when the cold plastic working materials are heated to about 60xc2x0 C. at the heating unit, it is preferable to set the temperature of the cooling air at lower than about 60xc2x0 C., more particularly in the range between 25 to 45xc2x0 C.
According to another aspect of the present invention, there is provided a lubricant coat forming apparatus for forming a dry coat of water dry type lubricant on the surface of each of cold plastic working materials. The apparatus includes a heating unit for heating the cold plastic working materials to a predetermined temperature, a lubricant applicator for applying the lubricant on the surfaces of the cold plastic working materials heated at the heating unit, a drying unit for drying the lubricant applied on the surfaces of the cold plastic working materials. The heating unit includes a plurality of storage chambers disposed at intervals for respectively storing the cold plastic working materials, a throw-in port through which the cold plastic materials are thrown into the plurality of storage chambers, and a discharging port through which the cold plastic working materials are discharged from the plurality of storage chambers. The plurality of storage chambers are adapted to travel along a circular path starting from the throw-in port and returning thereto via the discharging port. The heating unit further includes a heated air application means for applying heated air stream to the cold plastic working materials stored in the plurality of storage chambers, thereby heating the cold plastic working materials to a predetermined temperature.
With the above arrangement, the cold plastic working materials are successively thrown into the plurality of storage chambers through the throw-in port. The storage chambers with the cold plastic working materials therein travel along the circular path. During the travel, the heated air stream is directly applied to the cold plastic working materials to heat them to a predetermined temperature, and the cold plastic working materials are then successively discharged towards the lubricant applicator.
According to still another aspect of the present invention, there is provided a lubricant coat forming apparatus for forming a dry coat of water dry type lubricant on the surface of each of cold plastic working materials. The apparatus includes a heating unit for heating the cold plastic working materials to a predetermined temperature, a lubricant applicator for applying the lubricant on the surfaces of the cold plastic working materials heated at the heating unit, and a drying unit for drying the lubricant applied on the surfaces of the cold plastic working materials. The heating unit includes a plurality of storage chambers disposed at intervals for respectively storing the cold plastic working materials, a throw-in port through which the cold plastic materials are thrown into the plurality of storage chambers, and a discharging port through which the cold plastic working materials are discharged from the plurality of storage chambers. The plurality of storage chambers are adapted to travel along a circular path starting from the throw-in port and returning thereto via the discharging port. The heating unit further includes a means for immersing the cold plastic working materials stored in the plurality of storage chambers in a hot bath, thereby heating the cold plastic working materials to a predetermined temperature.
According to another aspect of the present invention, there is provided a lubricant coat forming apparatus for forming a dry coat of water dry type lubricant on the surface of each of cold plastic working materials. The apparatus includes a heating unit for heating the cold plastic working materials to a predetermined temperature, a lubricant applicator for applying the lubricant on the surfaces of the cold plastic working materials heated by said heating unit, and a drying unit for drying the lubricant applied on the surfaces of the cold plastic working materials. The heating unit includes a plurality of storage chambers disposed at intervals for respectively storing the cold plastic working materials therein, a throw-in port through which the cold plastic materials are respectively thrown into the plurality of storage chambers, and a discharging port through which the cold plastic working materials are discharged from said plurality of storage chambers. The plurality of storage chambers are adapted to travel along a circular path starting from the throw-in port and returning thereto via the discharging port. The heating unit further includes a means for immersing the cold plastic working materials stored in the plurality of storage chambers in hot water, thereby heating the cold plastic working materials to a predetermined temperature.
With the above arrangement, the cold plastic working materials are successively thrown into the plurality of storage chambers through the throw-in port. The storage chambers with the cold plastic working materials therein travel along the circular path. During the travel, the cold plastic working materials are immersed in the hot water to be heated to a predetermined temperature, and the heated cold plastic working materials are then successively discharged towards the lubricant applicator.